Resonant photoemission from the surface of a high-temperature Y---Ba---Cu---O superconductor
- Devyatov, V. G.
- Koshcheev, S. V.
- Cherkashin, A. E.
- Gluskin, E. S.
- Dudnikov, A. V.
- Dudnikov, V. G.
- Sood, A. K.
- Sahnie, V. S.
- Ventkataraman, G.
DOIAbstract
Photoemission measurements using synchrotron radiation are reported on YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-x</SUB> having a superconducting transition temperature of 90 K. The experiments were performed over a photon energy range of 40-161 eV as well as using Mg X-rays. An unusual enhancement of photoemission intensity associated with Ba(5p) and Ba(5s) levels was observed for a photon energy of ~104 eV. Our results suggest a different chemical composition of the surface and volume, two types of oxygen sites in the material, and a predominantly monovalent state of copper after Ar<SUP>+</SUP> etching
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